Safety switch



Nov. 9, 1937.

H. J. HAMMERLY SAFETY SWITCH Filed Nov. 15, 1936 3 Sheets-Sheet l INVENTOR AMMERLY,

Nov. 9, 1937. H. J. HAMMERLY SAFETY SWITCH Filed Nov. 13, 1936 3 Sheets-Sheet 2 MERLY,

INVENTOR fifi u m n a Patented Nov. 9, 1937 UNITED STATES SAFETY swrrcn Herman J. Hammerly,

New Britain, Com, as-

signor to The Trumbull Electric Manufacturing Company, Plainville, Conn, a corporation of Connecticut Application November 13, 1936, Serial No. 110,592

12 Claims.

My invention relates particularly to improvements in switches of the type in which there is a stationary contact and a switch member which slides with respect thereto.

The main object is to provide means for increasing the rupturing capacity of a switch of a given size. Specifically I have soughtto provide means for minimizing arcing upon breaking of the circuit-and protecting the switch against injury. The invention is especially directed-to switches of the knife blade type.

One object is to provide a construction of this type in which the circuit can be opened in the usual manner even when the connection between the operating crank and the switch blade is damaged.

In carrying out the invention I provide a construction in which the direction of flow of the arc is controlled. This is accomplished by enclosing the stationary contact and providing a definite passage or channel for the movement of the switch blade so that the arc is compelled to take up a definite movement whose direction is fixed by the construction of the associated parts.

The accompanying drawings illustrate some forms of construction embodying my invention.

Fig. 1 is a front view of a switch embodyin my invention, the cover being shown open and the switch in the closed circuit position.

Fig. 2 is a cross sectional view looking up wardly.

Fig. 3 is a vertical section and side view showing switch parts and guards or are snufiing means in the closed circuit position.

Fig; 4 is a fragmentary section on the plane of the line 4-4 of Fig. 3.

Fig. 5 is a section on the plane of the line 5-5 of Fig. 3.

Fig. 6 is a section and side view of the switch parts and guards in the open circuit position.

Fig. 7 is a perspective view of a switch blade and parts of the arc snuffer.

Fig. 8 isa view of the inside of a modified 5 housing.

Fig. 9 is a sectional view of the housing embodying two of the parts shown in Fig. 8.

Fig. 10 is a sectional view of another modificattion of my invention.

' Fig. 11 is a plan view of the housing and switch along one edge and provided with a catch 13 at the opposite edge. It should be understood that any suitable form of interlock may be provided. 0 The operating crank shaft I4 is suitably supported in or at opposite sides of the box and snap action mechanism I5 is preferably interposed between the crank shaft and the actuating handle l6.

The invention is shown as applied to a switch for a three-wire circuit but it will be necessary to describe only a single switch unit since the invention is applicable to a switch controlling. one or more circuits. Stationary contact or jaw 20 of any suitable character is mounted on an insulating support 2|.and provided with a circuit terminal 22. The switch blade 23 is hinged to a post 24 which is mounted on an insulating support 25 and provided with a suitable circuit terminal.

The are controlling or snufllng device is in the form of a housing preferably formed of two parts of insulating material 26 and 21 which may be secured together by fastening devices 28. This housing has at the bottom a recess 29 in which the stationary contact 20 is mounted. A slot 30 in the housing constitutes a narrow passage for the outer or swinging end of the switch blade 23. This passage is closed at the sides and has an exit at 3| from which the are or the pressure from the arc escapes when the circuit is opened. A number of pockets 3! may be provided in opposite sides of the passage 30 to increase the surface creepage distance for the are formed when the circuit is opened. Obviously one edge of the passage 30 must be opened to permit of the movement of the blade 23.

I provide, however, means for closing that part of this slot as the blade is moved away from the stationary contact. ing follower a which is secured to the blade 23 and projects beneath the blade and constitutes the means of connection between the crank shaft i4 and the switch blade.

For convenience inassembly this member 33 is provided with a notch 34 to accommodate the crank shaft. One edge of this member is formed on an arc whose center is the hinge axis of the blade 23 so that the insulating guard 33 follows the blade and substantially closes the side exit from the passage 30. The edge of the slot 30 is of corresponding arcuate form and bordered or flanked by flanges 36. These flanges prevent the are from blowing out through the slot 30. The

action will be understood by a comparison of the position of the parts in Figures 3 and 6.

This consists of an insulat This method of connecting the crank shaft l4 with the switch blade'has an additional important advantage in that the crank shaft can be actuated to open the switch even in case the connecting member" should be broken sincecover 35 for the, crank shaft so as to prevent any arc passing frome one switch blade to another along the crank shaft.

I may provide an insulating extension til at the outer end of each of the blade housings 2%, 217. By the use of such a deflecting member ii'l or otherwise controlling the direction of movement of the are it is possible to make the enclosure shallower than would be desirable if the arc was allowed to escape at right angles to the bottom of the box.

In the form of housing shown in Figs. 8 and 9 there is a chamber d ll which is tapered so as to in efiect choke the are as the blade moves to open circuit position. The walls may have small grooves ti to increase the area over which the arc must travel.

In the form shown in Figs. 10 and 11 there are two stationary contacts t5 each of which is enclosed by a housing M on all sides except at the slot M which is left for the switch blade w. The blade at is carried by an insulating plunger member 49 which slides between the housings. The housings are provided with flanges 5i] in which the plunger t9 moves so as to effectively prevent escape of an arc except at the outlet bl. The passage for the blade at may be like that of Fig. 5 or Fig. 9 or otherwise suitably formed.

It is important, however, that the are be confined so that it can not move in a direction to harm the switch. If an arc starts to form it can not escape except at a point remote from the stationary contact.

I claim:

1. A safety switch having a stationary contact and a hinged blade coacting therewith, and are snuffing means including an insulatinghousing for the stationary contact closed on all sides except for passage and exit of the swinging blade and insulating means having an arcuate edge following the blade alongside the housing and constantly close thereto as the blade moves to open the circuit.

2. In a safety switch, a stationary contact, a hinged blade coacting therewith, and are snufiing means including an insulating housing for the stationary contact closed on all sides except for passage of the swinging blade and insulating means following the blade alongside the housing leaving substantially no space for the escape of the arc except at the outer end as the blade moves to open the circuit, the insulating means extending beneath the blade and an actuating crank engaged n the insulating means beneath the blade.

3. A safety switch having a stationary contact and a hinged .blade coacting therewith, and are snuffing means including an insulating housing for the stationary contact closed on all sides except for passage of the swinging blade and insulating means having an arcuate edge carried by the blade and movable alongside the housing and constantly close thereto and closing said passage as the blade moves to open the circuit.

4. A safety switch having a stationary contact and a switch blade coacting therewith, and are snuifing means including'an insulating housing for the stationary contact closed on all sides except for passage of the switch blade and insulating means carried by the. blade and movable alongside and continuously close to the housing as the blade moves to open the circuit, and a crank shaft extending beneath said blade'on the aoaatva side opposite a the housing for actuating said blade.

5. In a safety switch, a stationary contact, a hinged blade coacting therewith, arc snufling means including an insulating housing for the stationary contact closed on all sides except for passage of the swinging blade and having a vent for escape of gases, and insulating means having an arcuate edge movable with the blade con.- stantly close to the housing and progressively closing the passage as the circuit is opened.

6. In a safety switch a stationary contact, a hinged blade coacting therewith, and are snumng means including an insulating housing enclosing the stationary contact but leaving a slot for passage of theswinging blade, and an insulating member having an arcuate edge carried by the blade and continuously closing said slot as the blade opens the circuit.

7. In a safety switch, a stationary contact, a hinged blade coacting therewith, and arc snufilng means including an insulating housing for the stationary contact closed on all sides except for passage of the swinging blade and an insulating link connected to the blade, the insulating link having an arcuate edge adjacent the housing and extending beneath the blade and an actuating crank engaged in the insulating link beneath the blade and on the side opposite to the housing.

8. In a safety switch, a stationary contact, a

movable blade coacting therewith, and are snuffing means including an insulating housing enclosing the stationary contact, insulating means progressively following the blade constantly close to and alongside the housing as the blade moves to open the circuit, and a crank shaft extending beneath said blade and on the side opposite to the housing for actuating said blade.

9. A safety switch having a stationary contact, a movable blade co-acting therewith, arc snuffing means including an insulating housing for i the stationary contact closed on all sides except for a passage for the moving blade, and insulating means attached to the movable blade and continually closing the passage upon opening movement of the blade.

10. A safety switch having a stationary contact, a movable blade co-acting therewith, arc snufling means including an insulating housing for the stationary contact closed on all sides except for a passage for the moving blade, and insulating means attached to the movable blade and continually closing the passage upon opening movement of theswitch, said housing being vented at a predetermined location to direct any escaping flash in a desired direction.

11. An electric switch having a stationary contact and a movable contact coacting therewith, an insulating housing for the stationary contact enclosing the contact in all directions except for movement of the movable contact and escape of an arc and an insulating member carried by the movable contact and progressively closing the, opening left by the movement of the movable contact.

12. An electric switch having a stationary contact, a housing therefor having a slot at one edge with an arcuate. edge, a hinged blade coacting with said contact and an insulating member moved by said blade and having an arcuateedge in close proximity to the arcute edge of the housing serving to progressively close said slot as the blade moves to open circuit position.

' HERMAN J. HAMMERLY. 

